Tone generator for an audio system



FIG. 1 is a top, front, and right-side perspective view of a tone generator for an audio system showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a right-side elevational view thereof;

FIG. 5 is a left-side elevational view thereof;

FIG. 6 is a top plan view thereof; and

FIG. 7 is a bottom plan view thereof. 

The ornamental design for a tone generator for an audio system, as shown. 